This invention relates generally to machining methods and apparatus and more particularly to methods and apparatus for abrasive waterjet machining of engineering materials.
The machinability number is a property of a specific material which varies depending on the type of machining operation, such as cutting, to be performed and is related to a number of materials properties. For abrasive waterjet machining of ductile materials, the machinability number is related primarily to flow stress of the material. For abrasive waterjet machining of brittle materials, the machinability is related to the fracture energy, grain size (or flow distribution for materials such as glass), modulus of elasticity and Poisson's ratio.
In a jobshop environment in which a variety of workpiece materials are cut using an abrasive waterjet machining process, if a new type of material is to be cut for the first time, a number of empirical cutting tests and calculations must typically be performed to determine the machinability number of the material prior to performing the cutting operation.
J. Zeng et al. in the paper titled "The Machinability of Porous Materials by a High Pressure Abrasive Waterjet," Proceedings of the Winter Annual Meeting of ASME, 1989, pp. 37-42, which paper is incorporated herein by reference, first introduced and incorporated the concept of a "Machinability Number" into parameter prediction methods for determining optimum Abrasive Waterjet (AWJ) machining criteria (e.g., abrasive particle flow rate and cutting speed) to be used in order to achieve a desired surface quality for different materials to be machined.
Some AWJ systems manufacturers and their customers have attempted addressing the problem of determining the machinability numbers of materials by providing databases of machinability number data from trial-and-error, empirical tests a performed by experienced AWJ operators on specific customer materials. This, however, involves considerable effort which is both costly and time-consuming. Such databases are also cumbersome and tedious to use.
The development of computer software has facilitated the use of databases of empirically obtained machinability number data to calculate the optimum operating criteria for materials for which the machinability number has been previously obtained.
In the case a new material for which the machinability number is unknown is to be cut or otherwise machined, the computer software may also be used to guide and assist an operator in conducting the empirical tests required to determine the machinability number from test pieces of the material.
The trial-and-error testing required to obtain machinability number data is wasteful, however, because it requires the use of numerous test pieces of material. Moreover, the testing is costly and time-consuming because it requires an AWJ machine operator to manually perform and evaluate the results of the testing, input the resultant empirical results, and program the machining parameters required for a subsequent machining operation to be performed.
The foregoing illustrates limitations known to exist in present machining methods and apparatus. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly a suitable alternative is provided including features more fully disclosed herein.